The invention relates to a hinge for constraining doors or hatches from a support structure.
In particular, the present invention relates to a hinge advantageously usable to constrain oven doors from ovens.
Conventional hinges are usually constituted by a box structure associated with the door, a lever pivoted at one of its ends internally to the box structure and associated with its other end to a support structure and a rod movable longitudinally internally of the box structures. One of the rod's ends is at an intermediate point of the lever and subjected to the action of elastic means anchored to the box structure.
The elastic means, whether of a traction type or a compression type, maintain the lever in one of at least two stable configurations; one configuration corresponds to the open-door situation and the other to the closed-door situation.
The lever emerges from the box structure through a respective longitudinal slot by means of its end which is to be associated with the support structure. Usually, for technical reasons connected with greater functionality, the lever is arranged in proximity to an end of the box structure and the extreme transversal edges of the slot act as end-run stops for the lever. In particular, the longitudinal wall of the box structure having the slot acts as an end-run stop for the lever in its closed-door configuration. The near transversal wall, which usually defines the slot, acts as end-run stop for the lever in its open-door configuration. Frequently the open door is used as a leaning surface for the dishes taken out of the oven, for example for checking the progress of the food being cooked. Considering that the temperature of the oven is usually rather high, instinctively the dish will be placed in proximity with the extreme edge of the door itself so that the user will feel less of the intense heat of the oven. Distancing the dish from the support structure, however, means increasing the moment of the weight that the dish exerts on the door, and ultimately, on the door support coinciding with the hinges.
When the door is in its open position, the hinge is kept in the corresponding configuration only by the transversal wall of the box structure on which the lever exerts a flexing force.
At present, the hinge box structure is obtained by means of bending or pressing of a rather thick steel sheet. Consequently, the transversal wall is made from the same sheet which is not mechanically resistant enough to flexion to ensure a sufficient degree of safety with regard to the flexing load.
On the other hand, the existing safety norms envisage that, when the door is in its extreme open position and a load is placed on it, the hinge must stand a load which is normally superior to the maximum flexion resistance of the transversal wall structured in the above-mentioned manner.
The simplest solution would seem to be that of strengthening the wall or making the box structure by casting, but that would be too expensive for the manufacturing companies as well as for the ultimate buyer.
Furthermore, the same hinges must be, in their open-door configuration, not only able to support a determined weight, but also sure to give way, more or less, when weights of an unforeseen but excessive (with respect to the predetermined maximum admissible weight) entity suddenly load on to the door.
With the aim of eliminating the possibility of this dangerous situation occurring, it has been proposed that there should be introduced, in the kinematic mechanism of the hinge, a weakening element with a predetermined breaking load, so that a load greater than the said breaking load would cause a giving of the weakening element itself and a consequent free rotation of the door, avoiding thus the toppling of the whole structure. Obviously, however, such a solution would bring about, in the case of such a breaking of the weakening element, the necessity of repairing the hinge through the substitution of the weakening element itself, with a consequent temporary withdrawal of the oven from use, and incurring considerable costs.